The first model developed by Uchatius was described as follows:
The pictures (a), (a) ... are painted on transparent glass and mounted on a disk, (A), at equal intervals, and the lowest of the pictures was illuminated from behind by the lamp (S) and the illuminating lens (B). A second disk, (C), contained the slits (b), (b) ... (the modern shutter) to be brought before each picture. The slits correspond to those in the Stampfer disk. Both disks are mounted on the same axis, (D), and are rotated by the crank (E). The slit, (c), corresponds to the pupil opening of the eye and the achromatic lens, (F), to the crystal lens of the eye. The lens is adjustable to allow the picture to be focussed sharply. The surface, (G) (the screen) finally corresponds to the position of the retina of the eye.
When the disks are turned, the successive pictures appear on the wall, (G), just as they are seen in the Stampfer disk, in intervals so short that they are not noticed by the eye.
This machine was satisfactory but limited. Uchatius was a sharp critic of his own work: “The apparatus produced very good motion pictures whose size, however, could be enlarged to a maximum of only six inches in diameter, because should the wall, (G), be moved far from the projector the pictures became too dark on account of the light cut off by the slits. And an enlargement of the slits brought about greater indistinctness. However, a projected motion picture had been attained which could be viewed simultaneously by a considerable number of people. But it still remained desirable to project this picture in a suitable size on a wall and thus show it in an auditorium or theatre.”
The first model had shown that the use of slits, even with the brightest light, could not result in a successful picture, according to Uchatius. (Illustration facing [page 105].)
He then constructed the improved model.
The pictures (a), (a) ... are painted transparently and set upright in a circle as close together as possible on the wooden slide (A). In front of each picture is a projection lens (b), (b) ... which can be inclined towards the center of the apparatus by means of a hinge and set screw. The inclination of all the projection lenses is so adjusted that their optical axes intersect at the distance at which the picture appears (in other words on the screen). It follows there that all the pictures must appear at one and the same point on the wall, (W).
The light source consists of a lime cylinder, (B) glowing in a stream of oxyhydrogen gas and the condensing lens, (C), which gives somewhat converging rays and illuminates only one picture at a time. The light is turned in a circle by a simple mechanism by means of a crank, (D), either rapidly or slowly as desired, (the first slow motion projector as well). During the movement the light source retains its upright position because of its own weight, since it is suspended from its support, (c), so as to be easily movable. The two rubber gas tubes rise and fall through the opened bottom of the cabinet. The lead weight, (E), serves as a counterweight to the light source.
Uchatius was pleased with this machine. “The result is now evident. The successively illuminated pictures appear on the wall in the same way as the so-called dissolving views but much more rapidly, thereby causing the effect of a moving picture. The size of the picture is not limited by the slits and the sharpness is not affected since no motion of the object picture occurs.”
In this manner Uchatius solved the problem of projecting these pre-film hand-painted motion pictures. In the very beginning of magic shadow projection Athanasius Kircher had sought the same results but did not have the apparatus or the knowledge of vision and movement necessary to carry out his wish. The lantern model of Zahn equipped with a revolving disk approximates the plan of Uchatius but failed, as did Kircher’s, and for the same reason. So far as Plateau was concerned, the illusion of moving images visible to one person at a time was sufficient. Anyway, the blind man—missing his own sight—probably did not feel impelled toward arranging simultaneous viewing for others. Doubtlessly he thought that to see motion pictures—one person at a time—was a sufficient marvel. Edison, more than half a century later, tended to the same opinion.